Evaluation of a software program for applying the American Board of Orthodontics objective grading system to digital casts

Introduction: The American Board of Orthodontics' objective grading system (ABO OGS) is currently the gold standard for evaluating plaster casts of completed orthodontic cases. Methods: Thirty-six cases of finished orthodontic casts in plaster and digital form were scored by using 2 methods: an electronic version of the ABO OGS designed to be used with digital casts (OrthoCAD, Cadent, Fairview, NJ) and the ABO gauge designed to be used with plaster casts. The 2 scoring methods were compared using descriptive analysis (range, absolute mean difference, and standard deviation), the Spearman rank correlation coefficient, and the Wilcoxon rank sum test. Results: Intraexaminer reliability was high for both the plaster and the digital casts (r = 0.998). A statistically significant difference (P <.001) was found when comparing the total ABO scores from the plaster and digital casts. The scores from digital casts exceeded the scores from plaster casts by an average of 9.0 ± 5.4 points. This difference was due to statistically significant differences in 3 ABO OGS components: alignment, occlusal contact, and overjet. Conclusions: The results indicate that this computer version of the ABO OGS cannot be used as a substitute for manual grading with the ABO ruler.